1. Field of the Invention
The present invention relates to a toilet bar suitable for topical application for cleansing the human body, such as the skin and hair. In particular, it relates to a toilet bar composition that is mild to the skin and which contains at least one latent acidifier.
2. The Related Art
The following all disclose laundry detergent bar compositions that contain various filler materials. U.S. Pat. No. 4,806,273 issued to Barone, et al. on Feb. 21, 1989 and U.S. Pat. No. 5,053,159 issued to Joshi on Oct. 1, 1991 disclose the use of various water insoluble fillers such as talc, calcium silicate, magnesium silicate, calcium sulfate, silica, bentonite, calcium phosphate and calcium carbonate in synthetic detergent laundry bars. U.S. Pat. No. 3,178,370 issued to Okenfuss on Apr. 13, 1965 discloses detergent laundry bar composition containing a broad range of salts. U.S. Pat. No. 4,705,644 issued to Barone, et al. on Nov. 10, 1987 also teach synthetic detergent laundry bars that contain various insoluble particulate materials and teach that calcium carbonate and talc are especially useful materials therein.
PCT publication no. WO98/06810 to Hauwermeiren, et al., published on Feb. 19, 1998 teaches laundry detergent compositions having filler salts selected from alkali and alkaline-earth metal sulfates and chlorides, with sodium sulfate as a preferred filler. PCT publication no. WO 98/38269 to Ramanan, et al., published on Sep. 3, 1998 discloses a laundry detergent bar with improved physical properties arising from the formation of a complex of calcium and the siliceous material in-situ. PCT publication no. WO 98/53040 to Ramanan, et al., published Nov. 26, 1998 discloses a laundry bar with improved sudsing and physical properties having a metal-anionic sulfonate surfactant complex.
The above patents and publications however, fail to disclose or suggest a mild to the skin toilet bar containing an effective amount of one or more specific latent acidifiers sufficient to provide pH reduction to the bar in the form of an aqueous slurry delta pH of about 0.5 or more, nor a Rys value (as defined below) in the range of about 0.70 to about 1.3. Aqueous slurry delta pH is herein defined as the value obtained when the pH of a 10% aqueous slurry of a bar with the latent acidifier is subtracted from the pH of an aqueous slurry of a bar without the latent acidifier. Rys is herein defined as the ratio of the yield stress of the bar containing the latent acidifier to the yield stress of the bar without the latent acidifier or,       R    ys    =            Yield      ⁢              xe2x80x83            ⁢      stress      ⁢              xe2x80x83            ⁢      of      ⁢              xe2x80x83            ⁢      bar      ⁢              xe2x80x83            ⁢      with      ⁢              xe2x80x83            ⁢      latent      ⁢              xe2x80x83            ⁢      acidifier              Yield      ⁢              xe2x80x83            ⁢      stress      ⁢              xe2x80x83            ⁢      of      ⁢              xe2x80x83            ⁢      bar      ⁢              xe2x80x83            ⁢      without      ⁢              xe2x80x83            ⁢      latent      ⁢              xe2x80x83            ⁢      acidifier      
Latent acidifiers are limited to organic or inorganic materials that when incorporated into a toilet bar do not substantially convert soaps or other alkaline materials contained in the bar to the free acid form and thus do not degrade the bar""s hardness as evidenced by yield stress measurements. As the bar is used with water, the latent acidifiers surprisingly either neutralize harsh soaps, or other alkaline materials contained in the toilet bar, or reduce the pH of the bar through other acid-base interactions, so as to create a mild cleansing action for the skin without substantially degrading the bar""s hardness. Latent acidifiers are further limited to compounds that do not release a gas with a change in pH and therefore do not include e.g. carbonates, bicarbonates, sulfites, and the like.
In one aspect the present invention is a toilet bar, having:
(a) about 0 to about 30% by wt.; preferably about 0 to about 20% by wt.; and more preferably about 0 to about 15% by wt. of a fatty acid soap;
(b) about 15 to about 60%; preferably about 20 to about 55%; and more preferably about 25 to about 50% by wt. of a non-soap anionic surfactant; and
(c) a latent acidifier in an effective amount to yield an aqueous slurry delta pH value of more than about 0.5, and preferably more than about 1.0.
In a preferred embodiment, there is at least about 0.1% by wt. of a fatty acid soap; preferably more than about 0.5% by wt.; and more preferably more than about 1.0% by wt.
In another aspect of the present invention is a toilet bar, having
(a) about 30 to about 80% by wt.; preferably about 40 to about 70% by wt.; more preferably about 50% to about 60% by wt. of a fatty acid soap;
(b) about 5 to about 40% by wt.; preferably about 7 to about 30%; more preferably about 10 to about 20% by wt. of a non-soap anionic surfactant; and
(c) a latent acidifier in an effective amount to yield an aqueous delta pH value of more than about 0.5, preferably more than about 1.0.
In a further aspect of the present invention is a toilet bar, having
(a) about 40 to about 85% by wt.; preferably 50 to about 80% by wt.; more preferably about 60 to about 75% by wt. of a fatty acid soap;
(b) about 0 to about 10% by wt.; preferably about 0 to about 7% by wt.; more preferably about 0 to about 5% by wt. of a non-soap anionic surfactant; and
(c) a latent acidifier in an effective amount to yield a delta pH value of more than about 0.5, preferably more than about 1.0.
In a preferred embodiment of this aspect of the invention, there is more than about 0.1% by wt. of a non-soap anionic surfactant; preferably more than about 0.5% by wt.; and more preferably more than about 1.0% by wt.